The present invention concerns novel norbornene derivatives of phenols and their use in polymeric compositions having improved ozone resistance.
Elastomeric vulcanizates are known to develop surface cracks when exposed to atmospheric influences and certain mechanical conditions. Such crack formation is caused by the presence of ozone. Elastomeric polychoroprene vulcanizates are particularly susceptible to ozone attack if subjected to mechanical stress and flex. Cracks are formed more readily at elevated temperatures.
To prevent crack formation, it is necessary to incorporate an antiozonant into the polymer composition.
It is known that polychloroprene vulcanizates may be protected against ozone-cracking by norbornene-type antiozonants. U.S. Pat. No. 3,563,947 discloses dinorbornene derivatives of alkyl-substituted benzenes and of other divalent organic radicals. Enol ethers of norbornene are described in U.S. Pat. No. 3,814,727 and acetals or ketals in U.S. Pat. No. 4,427,817.
However, various functionally active antiozonants often display adverse effects on the compounded or cured elastomeric article. A particularly undesirable effect is the tendency of polychloroprene compositions to develop undesirable color or staining. Only a few nondiscoloring antiozonants are commercially available. Now certain novel norbornene derivatives have been discovered that possess antiozonant and antioxidant activity as well as nondiscoloring properties in polychloroprene.